1. Field of the Invention
This invention relates to apparatus for sorting articles disposed in a random fashion across an article stream according to a predetermined physical characteristic, such as color, and, in particular, to sorting apparatus wherein electrical signals indicative of light reflected from articles to be sorted are multiplexed, divided, classified according to the ratio produced, and stored for a predetermined time period.
2. Cross-References to Related Applications
Subject matter disclosed herein is disclosed and claimed in the copending application of J. F. Lockett, Ser. No. 704,697, filed July 12, 1976, and assigned to the assignee of the present invention, and the copending application of J. D. P. Jones, E. H. Codding, M. A. Smither, and J. F. Lockett, Ser. No. 704,652 filed July 12, 1976, and assigned to the assignee of the present invention.
3. Description of the Prior Art
Sorting apparatus for separating articles in a random article stream utilize a variety of physical characteristics on which to base the sort. In one area of activity, the infield sorting of comestible products according to their reflected color characteristics, design activity of sorting apparatus has increased significantly in order to find alternatives to manual sorting. Such activity is economically justified by the increasing cost of in-field, manual labor previously utilized to sort acceptable from unacceptable products at the harvest site.
The sorting of comestible products according to their degree of ripeness is generally done on the basis of color differences between the ripe and the "green" products. U.S. Pat. No. 3,206,022 (Roberts) refers to one such color sorting machine in which apples are inspected, or viewed, and sorted according to their color characteristics at two selected wavelengths. This and other such color sorters, such as that described in U.S. Pat. No. 3,750,883 (Irving), however, require that the articles to be sorted be presented one at a time to a viewing zone or chamber for a color determination. The capacity of such sorters is limited by the need for singulation of the product. Although capacity can be increased by parallel operation of a number of such sorting machines disposed in side-by-side relationship, the cost is commensurately increased. In addition, such bichromatic color sorting machines are especially sensitive devices not suited to use in rugged harvesting environments. Further, the last-cited patent, due to its inability to reject foreign objects present in the product flow, totally vitiates its applicability to an infield environment.
Also, in the context of color sorting, various bichromatic optical devices have been developed which determine the color of articles passing through an inspection chamber or viewing zone. For example, U.S. Pat. No. 3,867,039 (Nelson), assigned to the assignee of the present invention, relates to an optical system for viewing a large area of a product stream and generating an electrical signal representative of the average color of the articles in the viewed area. This apparatus, however, is not a sorting machine and does not respond to remove unacceptably colored products from the product flow. This apparatus is intended for production process control applications, in which the average color of the product stream is used to control various process parameters.
The sorting apparatus disclosed and claimed in the copending application of M. Hoover and E. Codding, Ser. No. 588,219, filed June 19, 1975, now U.S. Pat. No. 3,980,181, and assigned to the assignee of the present invention, also relates to sorting based upon the reflected color properties of an article. This device operates to sort articles passing through the fields of view of a plurality of side-by-side viewing sections without any requirement of channelization. That is, a sorting of articles disposed randomly across a wide article stream is effected, based upon the wavelengths of visible light reflected from the articles. Further, any foreign objects carried randomly along in the article stream are classified and ultimately rejected.
Also known to the art are devices which base a sort upon physical characteristics of articles in an article stream other than their color.
One such device, intended for sorting a flow of articles randomly located across a wide path, is described in U.S. Pat. No. 3,872,306 (Palmer). In this patent, ionizing radiation is used to identify and separate dirt clods and stones from potatoes as the potatoes are harvested. This device operates on the absorbancy characteristics of articles within the article stream. Another device for sorting such a stream of articles is described in U.S. Pat. No. 3,179,247 (Hutter), in which the separation of rock salt from other matter is accomplished on the basis of differences in translucency. Neither of these devices are appropriate in the context of in-field product sorting based upon color criteria since neither includes any bichromatic color sensing elements. Further, the Palmer patent does not utilize a ratio signal to classify product. U.S. Pat. No. 3,901,388 (Kelly), is a further example of prior art sorting apparatus which does not utilize a ratio signal to classify articles to be sorted.
In most of the prior art sorting machines which provide a multichannel sorting capability, usually the circuitry for performing the viewing, classifying and ejecting is redundantly provided for each channel. Thus, each channel has associated with it all the necessary components to perform the recited functions. This redundancy unnecessarily increases the cost of these sorting machines.
It would therefore be advantageous to provide a sorting apparatus to sort articles randomly disposed in an article stream with a reduced number of circuit components. Further, it is advantageous to provide a sorting apparatus with a foreign object reject capability operable to eject foreign objects from the article stream. It is also advantageous to provide a sorting apparatus which includes an enabling mechanism to actuate the color and foreign object reject system only in the event that an article (the foreign object) has, in fact, passed the appropriate field of view.
The elimination of foreign objects, such as dirt clods, rocks, or the like, is a problem for some in-field sorting apparatus. In some prior art sorting machines, it is common practice to use light energy reflected from the product conveyor as a background intensity reference. However, it is found that the product conveyor becomes dirty or dusty as the sort progresses, thus vitiating the ability of the sorting apparatus to distinguish foreign objects, such as dirt clods, from products. It is, therefore, advantageous to provide a sorting apparatus which uses, as a reference background, a signal representative of an area other than the product conveyor.
Various prior art sorting apparatus utilize either the product conveyor or another suitably disposed member, both having predetermined reflectivity characteristics, to provide a background against which articles are detected. The prior art background also provides a reference signal against which articles are compared. It is advantageous, therefore, to provide a sorting apparatus which uses a non-reflective background region (a blackhole), against which articles are detected. It is also advantageous to provide a sorting apparatus which does not utilized the reflective characteristic of a background (either a conveyor or a separate member) to classify articles, but instead uses reference signal values otherwise generated.
Other prior art sorting apparatus, especially those providing a bichromatic sort, use only the magnitude of a signal representative of light reflected at one predetermined wavelength as the basis for a foreign object rejector. This has a tendency to eliminate certain acceptably colored products. It is therefore advantageous to provide a sorting apparatus for in-field sorting environments which uses the ratio of bichromatic signals as the basis for foreign object rejection.